1. Field of the Invention
The present invention relates generally to a process for reclaiming waste paper. In particular, the invention relates to a process for altering clay-coated paper for subsequent re-use. More particularly, this invention relates to a process of altering the ink imprinted upon many cellulosic materials and in particular to a process of altering a broad spectrum of printed products including newspaper, laser written paper, xerographic paper, rotogravure, headset, including coated and uncoated stock and particularly gloss multi-colored paper, such as magazines.
2. Prior Art
Conventional methods of reclaiming waste paper have principally involved various processes attempting to completely remove the ink. Many of these processes involved cooking of waste stock in various aqueous deinking chemicals. Such methods were reasonably satisfactory and adequate a number of years ago when there was no need to deink and reclaim waste paper having little or no quantities of ground wood. Such papers were printed with standard inks which are more readily removed or saponified with chemicals at elevated temperatures.
In recent years, however, methods of processing waste paper which involve cooking and the use of chemicals in aqueous media have become increasingly unsatisfactory for a number of reasons. Ink formations have become more and more complex and involve an increasing use of a wide variety of synthetic resins and plasticizers; with each ink having its own special formulation. Also, increasing amounts of synthetic resins and plasticizers were being used in a wide variety of sidings, coatings, plastic binding adhesives, thermoplastic resins and pressure sensitive label adhesives. Furthermore, the use of multicolored printing and multicolored advertisements have become increasingly popular in recent years and these involve a wide variety of new ink formulations. Many of the new ink formulations incorporate new pigments, dyes, and toners which are difficult to remove by conventional aqueous deinking chemicals. The former methods of deinking and reclaiming waste paper by chemical and cooking techniques are not adapted for, or adequate for, removing the new types of inks and coating resins. Due to high contents of thermoplastic resins, the softening action of heat and chemicals alone make their separation from the fibers very difficult. Additionally, the action of heat and chemicals tend to irreversibly set and more firmly bond some of the present day pigments to the fibers and fix dyes and toners to the fibers through staining.
Conventionally, cooking processes for deinking paper have utilized aqueous based suspensions. The stock to be salvaged is first thoroughly cleansed of superficial dirt and then macerated. The maceratum is boiled, subjected to cooking and defiberizing in a suitable aqueous alkali to soften the paper fibers, loosen and dissentegrate at least part of the ink and other matter adhering to the fibers, and thoroughly agitated, whether while in the alkaline solution or subsequently, to disintegrate and defiber the stock as thoroughly as possible. Thereafter, the pulp is riffled and screened and subsequently dewatered, preferably through suitable rolls, filters of the like, to remove a considerable portion of the loosened ink. It is then washed and dewatered for removal of additional quantities of the loosened ink as many times as may be practical and expedient.
In general, conventional deinking agents have employed an aqueous alkali solution which may, in addition, contain one or more of the following: a nonionic detergent, a sodium soap of fatty acids or abietic acid sulfonated oil, a dispersing agent to prevent agglomeration of the pigment after release and to emulsify any unsaponifiably material; a softening agent such as kerosine or mineral oil to soften the vehicle of the inks; an agent such as clay, silicate, etc., for selective absorption of pigments after release from the fiber to prevent redeposition on the fiber; and a basic exchange chemical to prevent formation of calcium soaps.
The cooked and defibered pulp is then diluted to less that 1 percent concentration and riffled and screened to remove oversized objects and undefibered pieces of paper. This material is then washed with large amounts of water, an average of 20,000 gallons of water per ton of pulp, to separate the fiber from other substances by washing or screening or by a flotation process. The disposal of large amounts of water used in such processes pose a stream pollution problem which must be remedied. Various patents have attempted to address this problem, including U.S. Pat. No. 5,362,362. However, such processes still rely upon similar techniques with similar problems. That is completely recycling the entire paper product.
Another area in which conventional processing techniques are unsatisfactory in reclaiming waste paper is in the area of electrophotography, better known as xerography. In the art of xerography, an electrostatic xerographic latent image is formed by uniformly charging a photoconductive insulating surface of a xerographic plate followed by exposing the charged surface to a pattern of light. The latent image formed by this technique is then developed with an electroscopic powder, also known as a toner, to form a powdered image which is then transferred to a sheet of normal bond paper. The powder image contained on the paper is then fused into the paper to form a permanent reproduction of an original image.
Another means of xerographic development is liquid electrophoretic development, which has particularly utility when photoconductive paper is xerographically processed. Developers may be prepared by dispersing finely ground pigments, such as zinc oxide, phthalocynanine blue or nigrosine in an insulating hydrocarbon liquid such as toluene, carbon tetrachloride, or petroleum fractions. The pigment particles acquire electrical charges during dispersion and remain suspended in a liquid. When a photoconductive paper containing an electrostatic image of a polarity opposite to that of the dispersed particles is immersed in the liquid, the pigment particles migrate and become fixed on the latent image.
Laser writing processes also employ various complex dyes and pigments applied to paper by high temperature fusion. These processes are similar in effect to the xerographic processes in that the ink removal is extremely difficult.
Since ever increasing amounts of xerographic and laser written paper are being used each year, effective processes for reclaiming this type of waste paper are very much needed. However, the effectiveness of any process must take into account the fact that development compositions for xerographic and laser writing processes consist of complicated organic compositions fused under high heat to the paper. With regard to toner development, as heretofore indicated, the toner is usually made of fusible resins or resin blends in which a pigment, such as carbon black, has been dispersed. The resins are selected to provide a melting point within the proper range for heat-fixing, or of a sufficient solubility for solvent vapor fixing. In essence, the action of heat and complex organic chemicals in these printing processed yield printed paper having almost irreversibly stained cellulosic fibers.
In the past, nonaqueous processes have been employed that utilize various chemical additives such as surfactants. U.S. Pat. No. 3,072,521, for example, relates to a nonaqueous process of deinking cellulosic materials employing a surfactant-containing organic solvent. The surfactant is necessary to enable removal of ink from the paper.
Other processes that have been developed utilize partial nonaqueous or immiscible solvents. U.S. Pat. No. 3,635,789, describes a deinking process whereby an immiscible solvent is added to an aqueous pulp suspension to facilitate the removal of ink from the pulp. U.S. Pat. No. 3,891,497, relates to a process for recovering of waste paper using steam and immiscible fluids and a small amount of water. The water is added to the waste paper to make it easier to break the bonds between the fibers. The process is conducted in a pulper at an elevated pressure because high temperatures are employed.
U.S. Pat. No. 5,217,573 also details a method of removing laser printer and xerographic toner, ink and the like. However, it also relies upon chopping and shredding the paper for subsequent recycling.
For the above and other reasons, conventional reclamation techniques used for recycling waste paper are no longer as efficient or effective as is desirable for many current needs.
In particular, for many applications, it is not necessary to completely remove ink from paper prior to paper re-use. On the other hand, because of significant potential liability for copyright and/or trademark infringement, it is desirable to alter any preexisting images on the reclaimed paper significantly prior to re-using. This need is not addressed by the known art.
The need for a satisfactory process for altering the ink upon paper to render the paper suitable for re-use has further become increasingly important due to greatly expanded utilization of paper and the increasing difficulty in disposal of the old papers especially due to a projected lack of future landfill sites. In this regard, and to preserve natural resources and minimize environmental problems, the need for developing useful and efficient paper re-using processes becomes of critical importance.